1. Field of the Invention
The present invention relates to an endoscope having a bending portion capable of being bent by wires, and particularly, to an improved technique of preventing meandering of the wires.
2. Description of the Related Art
An endoscope is composed roughly of an insertion portion inserted into an abdominal cavity or the like, and an operating portion to which a proximal end of this insertion portion is connected. In the insertion portion, a distal end including an image pick-up unit or the like, a bending portion which may be bent, and a long flexible portion which constitutes the proximal end of the insertion portion and is connected to the operation portion are sequentially connected toward the operating portion from the distal side. An operating mechanism for operating the bending portion provided in the insertion portion operates the bending portion by push and pull of wires which are arranged in a pair. As for the pair of wires, typically, a driving wire from the insertion portion and an operating wire from an angle knob that is an operating means are connected together within the operating portion (refer to JP-A-7-23892 JP-A-2003-290138).
FIG. 12 is a sectional view of an operating portion showing a connection structure in an endoscope.
A pulley 13 is provided inside an operating portion 11, and the pulley 13 is fixed to an angle knob (not shown), which is rotatably provided at a side portion of the operating portion 11, coaxially with a rotary shaft 15. A pair of operating wires 17a and 17b is wound around the pulley 13, and the operating wires 17a and 17b are pushed in the direction of the insertion portion 19, and are connected to one ends of angular pipe-shaped sleeves 21a and 21b that are wire-connecting members 21. Slip-off preventing members 23 (refer to FIGS. 13A and 13B) are respectively housed inside the sleeves 21a and 21b so as to be movable in an axial direction, and ends of the operating wires 17a and 17b are respectively connected to the slip-off preventing members 23. That is, the operating wires 17a and 17b are connected to the sleeves 21a and 21b with the play equivalent to the movement of the slip-off preventing members 23.
Ends of driving wires 25a and 25b are respectively fixed to the other ends of the sleeves 21a and 21b by nut members 27. A bracket 29 is fixed to the portion of the operating portion 11 on the side of the insertion portion 19, and the bracket 29 fixes wire-receiving members 31a and 31b which allow the driving wires 25a and 25b to be movably inserted therethrough. The driving wires 25a and 25b fixed to the sleeves 21a and 21b, respectively, are inserted through the wire-receiving members 31a and 31b, respectively, push in the direction of the tip through a flexible portion 33 of the insertion portion 19, and are connected to a bending portion (not shown) which becomes a distal end of the insertion portion 19. Thereby, when the angle knob is rotated, the operating wires 17a and 17b are pushed or pulled by the pulley 13, the driving wires 25a and 25b are pushed or pulled via the sleeves 21a and 21b correspondingly, and the bending portion of the insertion portion 19 is bent in a predetermined direction.
However, since the driving wires 25a and 25b and the operating wires 17a and 17b in the endoscope are connected via the sleeves 21a and 21b in the insertion portion 19, and the wires are exposed as they are between the wire-receiving members 31a and 31b and the sleeves 21a and 21b and between the sleeves 21a and 21b and the pulley 13, this connection structure is vulnerable to an axial compressive force. That is, as shown in FIG. 13A, when delivery resistance is stronger at the insertion portion 19 than the wire-receiving members 31a and 31b, the driving wires 25a and 25b between the wire-receiving member 31a and the sleeves 21a meandered due to deflection. On the other hand, as shown in FIG. 13B, when the movement resistance of the sleeves 21a and 21b is great, the operating wire 17a between the sleeve 21a and the pulley 13 meandered due to deflection. If such meandering is repeated frequently, there is a probability that the wires may be damaged by fatigue. In contrast, it is also conceivable that the wires are housed in tubes having rigidity in order to regulate meandering. However, when regions where the wires become naked are eliminated, play may not be given to wire length, and the flexibility of the insertion portion 19 may not be maintained. Additionally, if the sleeves 21a and 21b are interposed, the lengths of the driving wires 25a and 25b between the wire-receiving members 31a and 31b and the sleeves 21a and 21b change with the movement of the sleeves 21a and 21b. Therefore, the structure becomes complicated.